The Assembly is expected to pass the measure, which would limit California officers' cooperation with federal immigration enforcement, particularly the Secure Communities program.

A bill that that would restrict California law enforcement from cooperating with federal immigration enforcement efforts passed the state Senate on Thursday.

The Trust Act would prohibit police and sheriff's officials from detaining arrestees for possible deportation unless the suspects have previous convictions for a serious or violent felony. The measure is aimed at blunting federal immigration enforcement, in particular the Secure Communities program, under which fingerprints of arrestees are shared with immigration officials who issue hold orders.

The legislation now goes to the Assembly, where even opponents say it is likely to pass.

If signed into law, the measure would mark another in a string of state legislative efforts on behalf of California's estimated 2.55 million illegal immigrants.

The bill follows several months of controversy over whether Secure Communities can be imposed on local jurisdictions, some of which adopted rules to keep local law enforcement separate from immigration enforcement.

Advocates say the law will prevent illegal immigrants from being detained and possibly deported for relatively minor legal entanglements such as traffic infractions, misdemeanors and arrests that never led to a conviction. They argue that California should use such legislation to distinguish itself from such states as Arizona and Georgia, which have sought to crack down on illegal immigrants. Since last year, the Legislature has approved financial aid for undocumented students and voted to reduce impounds of vehicles driven by unlicensed drivers.

"Arizona and its governor may view all immigrants as criminals," said Chris Newman, legal director for the National Day Laborer Organizing Network, "but in California we have a different view."

The California State Sheriffs' Assn. opposes the legislation, saying that it puts local law enforcement in an untenable position between state law and federal policy.

"Now all of a sudden the sheriff has to make a decision based on this legislation, if it passes, on who [he] is and is not going to keep," said Curtis Hill, legislative representative for the association. "So is he following federal law? Or is he applying the California law?"

Regardless, Hill believes the bill will ultimately be approved.

"The reality is we don't see this bill being slowed down in any way, shape or form," he said. "We anticipate it will ultimately end up at the governor's desk and we'll see where it goes from there."

The governor has not said publicly whether he will sign the legislation.

More than 75,000 people have been deported from California through Secure Communities since the program began here in 2009, according to U.S. Immigration and Customs Enforcement.

Of those, 19,500 were convicted of misdemeanors, while 12,600 were convicted of non-aggravated felonies or multiple misdemeanors, and 23,500 were convicted of aggravated felonies or multiple other felonies. The rest were not convicted criminals but were considered priorities for deportation for other reasons, such as having been deported previously, ignoring a deportation order or overstaying a visa.

Several immigrant rights groups that fought unsuccessfully to stop Secure Communities have pushed legislation as the best option to blunt the program.

An earlier version of the Trust Act introduced by Assemblyman Tom Ammiano (D-San Francisco) sought to allow localities to opt out of Secure Communities by modifying an agreement between the state and federal government. But U.S. Immigration and Customs Enforcement Director John Morton terminated those agreements last year, making the legislation moot.

Ammiano introduced the latest version earlier this year.

"So many people in the immigrant community contribute so heavily to our economy, to our schools, to the military," Ammiano said, "they deserve better treatment than being rounded up or hounded or being intimidated so that they can't report criminal activity."

Under the law, which passed the Senate on a 21-13 vote, an arrestee who is not convicted of a serious or violent felony would be released after serving a sentence, posting bond, being acquitted of charges or otherwise becoming eligible for release,even if immigration officials request that the person be held for possible deportation.

Blanca Perez, 33, who sells paletas from a cart in Los Angeles County, was arrested last year on suspicion of illegal street vending. After spending several days in jail, she was transferred to immigration detention. She was placed in deportation proceedings and released wearing an ankle bracelet. The bracelet was later removed, but whether she will be allowed to remain in the country is unclear.

Earlier this year, she testified about her experience before the Senate Public Safety Committee.

"The police need to leave us in peace," she said. "They should let us work in peace."